Sound recorder and reproducer



Jan. 10, 1956 E. STEED 2,730,369

SOUND RECORDER AND REPRODUCER Filed July 6, 1951 2 Sheets-Sheet 1- ATTORNE Jan. HQ, 155 STEED SOUND RECORDER AND REPRODUCER 2 Sheets-Sheet 2 Filed July 6, 1951 United States Patent-O SOUND RECORDER AND REPRODUCER Edgar L. Steed, Poughkeepsie, N. Y., assignor to Daystrom Electric Corp., Poughkeepsie, N. Y., a corporation of Delaware Application July 6, 1951, Serial No. 235,506

1 Claim. (Cl. 274-13) This invention relates to microgroove sound recording and reproducing apparatus in which a sound track is cut or embossed on a recording medium of endless loop form, typically a film of cellulose acetate or similar material. The sound track is formed in a continuous path by the stylus of a recording head or transducer continuously moved transversely of the film which is advanced longitudinally past a fixed recording station. A playback head or transducer may be conveniently provided adjacent the recording head for motion therewith. As from 400 to 600 or more grooves may be cut per inch, the relative lateral positions of the film and recording head must be closely controlled. For this purpose, the recording head is sup ported in a carriage which is coupled to a lead screw cut on a shaft journaled in a frame with reference to which the lateral position of the film is fixed.

The present invention provides accurate location of the recording stylus relative to the film by means of an improved support and guide system for the carriage employing a single rail or channel in the frame to define a line of motion for the carriage, a backlash free coupling between the carriage and the lead screw, and an improved support for the lead screw shaft uniquely defining its position along its own length with reference to the frame.

The invention of the present application represents an improvement over that shown and claimed in the application of Marvin F. Royston, John P. Drinjak and John L. Petz, Serial No. 174,456, filed July 18, 1950, and assigned to the assignee hereof.

In the accompanying drawings:

Fig. 1 is a partial plan view of a sound-on-film recording and reproducing machine according to the present invention; I

Fig. 2 is a sectional view in elevation taken on the line 22 of Fig. 1;

Fig. 3 is a sectional view in elevation taken on the line 3-3 of Fig. 2; V

Fig. 4 is a sectional view in elevation taken on the line 4-4 of Fig. 2;

Fig. 5 is an enlarged elevational view of the bracket illustrated in Fig. 2 for coupling the transducer head carriage to the lead screw, together with certain associated elements of mechanism;

Fig. 6 is a plan view of the bracket of Fig. 5, and

Fig. 7 is a detailed view in section showing the bearings for the lead screw shaft.

The sound-on-film recording and playback machine shown in plan in Fig. l is a self-contained unit including recording and playback heads or transducers, drive mechanism for advancing the film past a recording station, indexing mechanism for advancing the transducers crosswise of the film at the recording station, and electrical amplifying equipment for translating the voice currents of a microphone into electrical oscillations adequate to drive the stylus of a recording head or transducer and for translating the weak oscillations induced by a playback stylus in its associated playback head into currents adequate to drive a loud-speaker.

2,730,369 Patented Jan. 10, 1956 In Fig. 1 a recording medium is shown as a film 10 having the form of an endless loop. The film passes over a driving roller 12 where it is engaged by styli of a transducer carriage generally indicated at 28. Suitable pres sure rollers or shoes 16 and 17 maintain the film in en gagement with the driving roller 12 to move it past the recording station thereat at which the styli of the carriage 28 engage it.

The carriage 28 includes a plate 84 from which the recording and reproducing transducers are supported within a housing 126, and the carriage as a whole is advanced transversely of the film by means of a lead screw 18 to which the carriage is coupled as will be subsequently described. The lead screw is cut on a shaft 19 mounted for rotation in a frame 20 at bearings 22 and 24. The lead screw is rotated by means of a motor 26. The motor friction pinion 27 drives a friction wheel 30 whose shaft 32 carries a worm thread 33 engaging a worm wheel 34. The shaft 32 also carries the film driving roller 12. The worm wheel 34 is pinned to a stub shaft 36 carrying a worm 38 which engages a worm Wheel 40 afiixed to the lead screw shaft 19. The stub shaft 36 is journaled in a frame member 37 which floats on drive shaft 32 between the bearing 31 and a collar 35. The position of the carriage 28 is indicated at the front panel 21 by means of a divided head 42 which is coupled to the carriage by means of a capstan 118 which engages a wire 120 strung between pins 122 and 124 afiixed to the plate 84.

The carriage support is shown in further detail in Figs. 2 and 3. A vertical member 23 integral with the frame 29 has afiixed thereto a channel member 46 provided with V-shaped grooves 48 and 50 open respectively upwards and downwards. The grooves 48 and 50 accommodate balls 54 on which the carriage rolls in its motion under the influence of the lead screw. As indicated in Fig. 2 the grooves 48 and 50 are blocked at the ends of the channel member 46 by pins 53 and need not be completed through the center section of the member. The grooves 48 and 50 are to a first approximation parallel, but the construction of the invention compensates for any minor lack of parallelism between them, preventing rocking of the carriage and insuring a unique location for it in planes perpendicular to the lead screw shaft for every point of its travel.

The carriage plate 84 has afiixed to its lower edge a' channel member 56 having formed therein a groove 58 complementary to the groove 50. With two balls 54'engaged between them, the grooves 50 and 58 define the line of motion of the carriage. An additional grooved channel member 60 is resiliently coupled to the carriage plate 84 in position to bear against additional balls 54 moving in the groove 48.. The channel member 60 thus' serves to stress the carriage against the frame at the grooves 50 and 53, and to retain the carriage in proper position about the axisof motion defined by the groove 50.

The movable channel member 60 is provided with'a lateral flange 61 which bears against the plate 84.

Through an oversized hole 63 in flange 61 a screw 65 is threaded into the plate 84 and carries between its head and the flange 61 a spring 68 to retain the flange in contact with the plate 85. Screws 70 threaded into an abutment 62 afiixed to the plate 84 force a leaf spring 64 down over the screw 65 into contact with the upper surface of the movable channel member 60 and stress it against the balls 54 which ride between it and the fixed channel member 46. Accordingly the movable channel member 60 can undergo both rotational and translational motions over the surface of the plate 84 and is thus able to adjust to any lack of parallelism between the grooves 48 and 50 in frame channel member 46. The resilience of the spring and freedom of the channel member 60 give an approximately equal loading to all four of the balls, protecting 3 them from the formation of flats and insuring a smooth travel for the carriage.

The direction of motion of the carriage is established by the orientation of the groove 50 in channel member 46. Groove 50 possesses a fixed orientation in the frame of the machine. In the assembly of the machine care is taken to establish the channel member'46 in such a position as to place its groove 50 in approximate parallelism with the shaft 32 to which the driving roller 12 is affixed. An exact parallelism is not essential because the recording and playback heads are pivotally mounted within the housing 126 for rotation about axes approximately parallel to the direction of motion of the carriage.

The motion of the carriage is determined by rotation of the lead screw 13, and a flexible coupling is required between the lead screw and the carriage to compensate for possible lack of parallelism between the lead screw shaft, and the path of motion of the carriage. For this purpose the invention provides acoupling which eliminates backlash between the carriage and the lead screw and which accommodates any lack of parallelism between the lead screw and the path of the carriage. The coupling is a frictional one so that the carriage may be manually adjusted to any desired position crosswise of the film by means of the handwheel 42.

Referring to Figs. 2, 4, 5 and 6, the carriage is coupled to the lead screw by means of a bracket 102 and toothed wheel 104 frictionally engaged therewith. The plate 84 carries on the side adjacent the lead screw two bosses 106 which are bored on their adjacent faces to receive the lugs or trunnions 108 of an expansible bracket 102. The lugs 108 are formed at the ends of a pair of wings 112 which connect with the remainder of the bracket through con strictcd portions 114. A slit 116 between the wings gives them resilience with respect to each other, and an aperture 5 117 is cut in the slit to receive a tapered screw 119 by means of which the wings can be spread by an accurately controlled amount to eliminate side play of the bracket with respect to the carriage plate 84.

The toothed wheel 104 is mounted on a stub shaft 121 (Fig. 5) passing through a flange 103 on the bracket inclined .to its wings 112. A spring washer 123 and lock nuts 125 and 127 make possible the control of the frictional engagement between the worm wheel and the bracket. By suitable adjustment of the tension at the spring washer 123, the carriage may be caused to move crosswise of the film as the lead screw 18 rotates while permitting broad motion of the carriage at the handwheel 42 in manually setting the carriage to a desired portion of the film. The wheel 104 is maintained in engagement with the lead screw by means of a tension spring 130' strung between the bracket 102 and the plate 84 as shown in Fig. 5.

In operation, whether for recording or playback, the carriage is advanced always in one direction, from the backlto the front of the machine in the embodiment shown, i. e. towards the bottom of the sheet in the plan view of Fig. l. The recordings are often made discontinuously. As a result a thrust is alternately applied to and removed from the lead screw shaft by the carriage. It is therefore desirable to give the lead screw shaft a fixed bearing against which to abut in carrying the load in advancing the carriage but to eliminate all end play so that thesound groove in the film may be continuous despite starts and stops in the recording process. At the same time provision must be made for thermal expansion and contraction of the frame. To this end the lead screw shaft is given a fixed bearing at the back of the frame and a resiliently movable bearing at the front. These bearings are illustrated in Fig. 7.

The fixed bearing generally indicated at 22 comprises a shallow bore or recess 73 formed in the frame 20, receiving the end of the lead screw shaft. For reduction of friction it is desirable to give a rounded approximately spherical shape to the end of the shaft, and a disk 74 of hard fibrous material is inserted in the bore 73 to receive the shaft. At the front end of the machine the lead screw shaft bearing generally indicated at 24 is supported within a bore 76 extending through a portion of the frame 20. The bore '76 may be closed by means of a movable plate 78 pinned to the frame at 80. The front end of the lead screw shaft is received in a bearing cup 82 which is retained against the shaft by means of a helical spring 83 stressed between the cup and the closing plate 78.

in the embodiment which has been described the channels or grooves of the frame which support the carriage by means of ball bearings have been shown as formed on a single member 46. These can of course equally well be formed on separate members both aflixed to the frame. in addition the coupling between the bracket 102 and the carriage has been shown as two pivot blocks affixed to the carriage into which trunnion-like pins on the wings of the bracket protrude. Any other form of pivot bearing may equally well be used.

I claim:

In a sound-on-filrn recorder including a frame and a carriage supporting a recording head for motion transversely of afilm at a recording station fixed with reference to the frame, a carriage drive comprising a lead screw shaft, bearings in the frame for said shaft, two channels fixed with respect to the frame substantially parallel to each other and to the lead screw shaft, a channel affixed to the carriage, a channel movably supported on the carriage, a plurality of balls engaged between one of the frame channels and the fixed carriage channel, a plurality of balls engaged between the movable carriage channel and the other frame channel, a spring stressed between the carriage and the movable carriage channel urging the-movable carriage channel toward the frame channel associated therewith, two. bearing members atfixed to the carriage along a line substantially parallel to the fixed carriage channel, a bracket, wings on said bracket adapted to en gage said carriage bearing members, means to adjust the spacing of said wings, and a toothed wheel frictionally coupled to said bracket in position to engage the thread of the lead screw.

References Cited in the file of this patent UNITED STATES PATENTS 672,337 Stanley Apr. 16, 1901 1,979,829 Gramann Nov. 6, 1934 2,463,5l3 Brubaker Mar. 8, 1949 2,530,029 Pond Nov. 14, 1950 2,573,303 Bozoky Oct. 30, 1951 

